The present invention relates to spring probe assemblies of the type used in ATE (Automatic Test Equipment) and other industries which require testing of integrated circuits and specifically to spring probe assemblies to be used at microwave frequencies (10 GHz+).
Spring probe assemblies are extensively used in the ATE industry, as well as other industries, which require testing of integrated circuits, silicon wafers, etc. in order to provide temporary contact to planar devices such as DUT (Device Under Test) boards in order to interrogate the various inputs and outputs of the integrated circuits which are plugged onto the DUT board for test. Conventional spring probe assemblies use spring pins in the ground and signal positions which create impedance mismatches when disposed upon the planar device. These impedance mismatches seriously limit the frequency at which the integrated circuits under test can be interrogated. For this reason, the conventional coaxial spring probe was designed to compensate for much of this impedance mismatch by providing a coaxial ground tube which provides an impedance match, around the signal pin, for the majority of the spring travel, during test implementation. While the impedance mismatch, using a coaxial spring probe, is improved, a typical coaxial spring probe still has limitations due to impedance mismatches of the materials, internal to the coaxial spring probe, which hold the coaxial spring ground tube and the signal spring pin in place. These mismatches typically limit frequency performance to under 6 GHz. A coaxial spring probe having better controlled impedance mismatch is highly desirable.